Pelvis and Perineum 1.2

Question 1

What type of muscles are the muscles of the male perineum?

Answer 1

skeletal

Question 2

What are the muscles in the male perineum innervated by?

Answer 2

by the pudendal nerve and its branches

Question 3

What do most of the muscles of the male perineum have attachments to?

Answer 3

central tendon of the perineum (perineal body)

Question 4

What is the perineal body in men?

Answer 4

a midline structure located just anterior to the anal canal and just behind the bulb of the penis

Question 5

What is the subdivision of the perineum?

Answer 5

1. Anterior urogenital triangle

2. Posterior anal triangle

Question 6

How are the two triangles divided?

Answer 6

imaginary horizontal line connecting the 2 ischial tuberosities divides the perineum into these 2 descriptive triangles

Question 7

What do the ischiocavernosus and bulbospongiosus muscles cover

Answer 7

• crus of the penis (corpus cavernosum) and the bulb of the penis (corpus spongiosum)
• these bodies are the erectile tissue of the penis

Question 8

What does contraction of the bulbospongiosus muscle help?

Answer 8

helps to evacuate any remaining urine in the spongy urethra

Question 9

Where does the external urethral sphincter muscle arise from?

Answer 9

ischiopubic ramus

Question 10

Where does the external urethral sphincter muscle insert?

Answer 10

into a median raphe and the perineal body and extends superoanteriorly along the prostate to the neck of the urinary bladder

Question 11

What is the action of the external urethral sphincter muscle?

Answer 11

acting together, the urethral sphincter muscles on both sides form a sphincter that compresses the membranous portion of the male urethra

Question 12

What is the innervation of the external urethral sphincter muscle?

Answer 12

perineal branch of the pudendal nerve (S2-S4)

Question 13

What forms a true sphincter of the urthera (external urethral sphincter) in men?

Answer 13

only a portion of the muscle

Question 14

What does another portion of the muscle form?

Answer 14

• extends vertically to the bladder and invests the prostatic urethra anteriorly and laterally
• unknown how or whether this muscle acts on the prostatic urethra.

Question 15

What is at the neck of the male urinary bladder?

Answer 15

an internal urethral sphincter

Question 16

How is the internal urethral sphincter innervated?

Answer 16

smooth muscle, sympathetically innervated from L1-L2

Question 17

Why is the internal urethral sphincter important during ejaculation?

Answer 17

it prevents semen from entering the urinary bladder or urine from entering the prostatic urethra

Question 18

What is erectile dysfunction?

Answer 18

an inability to achieve and/or maintain penile erection sufficient for sexual intercourse

Question 19

What does sexual stimulation normally release?

Answer 19

1. nitric oxide from nerve endings and vascular endothelial cells
2. thus relaxing the smooth muscle tone and increasing blood flow
3. which then compresses the veins draining the erectile tissues
4. allows for engorgement of the tissues

Question 20

What do drugs that treat ed aid?

Answer 20

relaxation of the smooth muscle

Question 21

What does the external anal sphincter surround?

Answer 21

the last 2 cm of the anal canal

Question 22

What does the external anal sphincter consist of?

Answer 22

consists of subcutaneous, superficial, and deep portions

Question 23

What are the attachments of the external anal sphincter?

Answer 23

1. Some fibers attach anteriorly to the perineal body and posteriorly to the anococcygeal ligament
2. Fibers also may join the superficial transverse perineal, the levator ani, and the bulbospongiosus muscles
3. Deep fibers interlace with the puborectalis muscle.

Question 24

What is the action of the external anal sphincter?

Answer 24

• muscle is in a tonic state of contraction and has no antagonist
• keeps the anal canal closed

Question 25

What is the innervation of the external anal sphincter?

Answer 25

inferior rectal branches (largely S4) of the pudendal nerve (S2-S4)

Question 26

Where is the internal sphincter?

Answer 26

lies deep to the external anal sphincter (that is, just superior to the external anal sphincter)

Question 27

What is the control of the internal anal sphincter?

Answer 27

smooth muscle sphincter involuntary control

Question 28

What type of fibres maintain its tonic contraction?

Answer 28

sympathetic

Question 29

What do parasympathetic fibers do?

Answer 29

• relax muscle tone and permit expansion of the anal canal during defecation or flatulence
• this action also requires that the external anal sphincter be relaxed simultaneously

Question 30

What can trauma to the anal mucosal lining (e.g. from compacted faeces) lead to?

Answer 30

anal infection that can spread into the adjacent sphincter muscles and beyond, into the ischioanal fossae of the fat-filled anal triangle

Question 31

What is the female pelvic viscera innervated largely by?

Answer 31

lower portion of the parasympathetic division of the autonomic nervous system

Question 32

How do these parasympathetic preganglionic fibres arise?

Answer 32

as the pelvic splanchnic nerves from the nerve roots of S2, S3, and S4

Question 33

Where do many of these preganglionic parasympathetic fibres synapse?

Answer 33

in the inferior hypogastric (pelvic) plexus, adjacent to the rectum, uterus, ovary, and uterine tubes

Question 34

Where does postganglionic parasympathetic from the inferior hypogastric plexus course?

Answer 34

to the respective pelvic viscera

Question 35

What do pain afferents from ovaries, uterine tubes and fundus and body of uterus follow?

Answer 35

sympathetic fibers back to the spinal cord (T11 or T12 to L1-L2 levels)

Question 36

How do pain fibers from the uterine cervix and vagina (subperitoneal structures) travel back to the spinal cord?

Answer 36

via the pelvic splanchnic nerves (S2-S4)

Question 37

Where do cell bodies for these pain afferents reside?

Answer 37

in the spinal (dorsal root) ganglia of the respective spinal cord levels

Question 38

Where is pain from the pelvic and perineal viscera is felt over?

Answer 38

the dermatome areas T11-L2 and S2-S4; it is largely confined to the hypogastric region, pelvis, and perineum and occasionally radiates into the upper part of the lower limb

Question 39

What does the pudendal (somatic) nerve innervate? (W)

Answer 39

skin and skeletal muscle of the female perineum and external genitalia

Question 40

Where does the pudendal nerve arise from? (W)

Answer 40

anterior rami of S2, S3, and S4 spinal cord levels

Question 41

What does the pundeal nerve do after emerging from the pudendal (Alcock’s) canal? (W)

Answer 41

• divides into inferior anal (rectal) nerves
  1. the perineal nerve
  2. the dorsal nerve of the clitoris

Question 42

Where do parasympathetic fibers arise from? (W)

Answer 42

S2-S4 levels

Question 43

Where do the parasympathetic fibres travel? (W)

Answer 43

travel in pelvic splanchnic nerves to the inferior hypogastric plexus and uterovaginal plexus

Question 44

What do the parasympathetic fibres stimulate in the women?

Answer 44

1. vaginal secretions
2. erection of the clitoris
3. engorgement of the bulbs of the vestibule (vasodilation of the arteries supplying the erectile tissue of the crus of the clitoris, clitoris, and vestibular bulb)

Question 45

How do you achieve local anaesthesia of the perineal area?

Answer 45

1. pudendal nerve may be blocked selectively
2. by infiltrating a local anesthetic into the region of the pudendal canal
3. thus numbing the S2-S4 somatic region (skin and skeletal muscle) of the perineum